A thin film forming process for forming a thin film of a metal or an insulating material on a substrate is indispensable in the manufacture of a semiconductor device such as an IC or a liquid crystal display device. A film forming method using a sputtering apparatus is used in the thin film forming process. In this film forming method, a target made of a raw material for a thin film formation is used; and an argon gas or the like is excited into plasma by a DC high voltage or a high frequency power; and the target is activated by the gas excited into plasma and is sputtered; and then it is deposited on a target substrate.
A film forming method using a magnetron sputtering apparatus is mainly employed as a sputtering film forming method. In this film forming method, to achieve a high film forming rate, magnets are arranged on a rear surface of a target such that magnetic force lines are generated in parallel to each other on a target surface, thereby confining plasma on the target surface and thus obtaining high-density plasma.
FIG. 14 is a configuration view illustrating major components of such a conventional magnetron sputtering apparatus. In the figure, a reference numeral 101 denotes a target; 102, a target substrate on which a thin film is to be formed; 103, a plurality of magnets; 104, magnetic force lines; and 105, a target 101's area which is eroded, i.e., an erosion area.
As shown in FIG. 14, the plurality of magnets 103 are arranged on a rear surface of the target 101 such that their N and S poles are oriented toward predetermined directions. High frequency power (RF power) 106 or DC high voltage power 107 is applied between the target 101 and the substrate 102, so that plasma is excited on the target 101.
Meanwhile, the magnetic force lines 104 oriented from N poles to their adjacent S poles are generated from the plurality of magnets 103 installed on the rear surface of the target 101. A horizontal magnetic field (a magnetic force line component parallel to a target surface) is maximized locally at a position on the target surface where a vertical magnetic field (a magnetic force line component perpendicular to the target surface) is zero. In an area where the horizontal magnetic field component is great, electrons are confined in the vicinity of the target surface, so that high-density plasma is obtained. As a result, the erosion area 105 is formed around this area.
Since the erosion area 105 is exposed to the higher-density plasma compared to the other areas, consumption of the target 101 tends to be great thereat. As a film formation is continued, a target material is consumed in this area, so that the entire target has to be replaced. As a result, the efficiency of the usage of the target 101 may be deteriorated. Besides, as for the thickness of a thin film on the target substrate 102 installed to face the target 101, since a film thickness at a position corresponding to the erosion area 105 is thicker than film thicknesses at the other areas, the uniformity of the entire film thickness of the target substrate 102 may also be deteriorated.
Conventionally, there have been proposed methods in which a bar magnet is used as a magnet for generating magnetic fields, and the bar magnet is moved and rotated to move an erosion area as time passes, so that a local consumption of target is substantially suppressed. That is, a time average of target consumption is uniform and the uniformity of the film thickness of a target substrate is improved (see, for example, Patent Documents 1 to 3).
In these methods, each bar magnet has a configuration in which an N pole and an S pole are respectively positioned at surfaces opposite to each other in its diametric direction while the same magnetic polarities are respectively arranged in parallel in its lengthwise direction, or an N pole and an S pole are respectively positioned at surfaces opposite to each other in its diametric direction while the same magnetic polarities are respectively arranged in a spiral shape in its lengthwise direction. Further, stationary bar magnets are positioned in the vicinity of moving or rotating bar magnets so that a closed circuit is formed at an erosion area within the target. Each of these stationary bar magnets has a configuration in which an N pole and an S pole are respectively positioned at surfaces opposite to each other in its diametric direction while the same magnetic polarities are respectively arranged in parallel in its lengthwise direction.
In addition, there has been also proposed a method in which a plurality of film-formation rotary magnets buried in a spiral shape is used to continuously form waves of a magnetic field (see, for example, Patent Document 4).
Patent Document 1: Japanese Patent Laid-open Publication No. H5-148642
Patent Document 2: Japanese Patent Laid-open Publication No. 2000-309867
Patent Document 3: Japanese Patent No. 3566327
Patent Document 4: Japanese Patent Laid-open Publication No.